Fever in Adults Causes

Viral fever

Illnesses caused by viruses are among the most frequent causes of fever in adults. Symptoms can include a runny nose, sore throat, cough, hoarseness, and muscle aches. Viruses also may cause diarrhea, vomiting, or an upset stomach.

For the most part, these viral illnesses will improve simply with time. Antibiotics will not treat a viral infection. Symptoms can be treated using decongestants and anti-fever medications bought over the counter. If diarrhea or vomiting occurs, then the person needs to be encouraged to drink fluids. Gatorade or sports drinks will help replace lost electrolytes. If fluids are not staying down, then medical care should be sought. Viral illnesses can last as long as one to two weeks.

The influenza virus is a major cause of death and serious illness in the elderly. Symptoms include headaches and muscle and joint aches, as well as the other common viral symptoms, including fever. Vaccines against seasonal influenza as well as H1N1 influenza are available. Also, antiviral medications can be administered to fight the influenza virus immediately after the symptoms start. This illness usually occurs during the winter.

Bacterial fever

Bacterial illnesses causing fever can affect almost any organ system in the body. They can be treated with antibiotics.

Central nervous system (brain and spinal cord) infections can cause fever, headache, neck stiffness, or confusion. A person may feel lethargic and irritable, and light may irritate the eyes. This could represent meningitis or a brain infection, so the person should go immediately to the doctor.

Upper respiratory system infections occur in the throat, ears, nose, and sinuses. A runny nose, headache, cough, or sore throat accompanied by a fever may indicate a bacterial infection, but a viral infection is the most common cause.

Infection of the genitourinary system may cause a person to have a burning sensation when urinating, blood in the urine, the urge to urinate frequently, and back pain along with a fever. This would indicate an infection in the bladder, kidney, or urinary tract. Antibiotics would treat such an infection.

If the reproductive system is affected, people often see a discharge from the penis or vagina and have pelvic pain along with the fever. Pelvic pain and fever in women may represent pelvic inflammatory disease (PID), which can cause significant damage to the reproductive organs. In this case, the person and any sexual partners should see a physician.

Gastrointestinal system (digestive system) infections are indicated by diarrhea, vomiting, stomach upset, and sometimes blood in the stool. Blood in the stool can indicate a bacterial infection or other type of serious illness. Abdominal pain may be caused by an infection of the appendix, gallbladder, or liver, and medical care should be accessed.

The circulatory system (including the heart and lungs) can be invaded by bacteria. There may not be any specific symptoms with the fever. A person may feel body aches, chills, weakness, or confusion. The condition known as sepsis is present when bacteria enter the bloodstream. An infection of a heart valve with resulting inflammation (endocarditis) can occur in people who had heart surgery in the past and in people who use IV drugs. This condition requires hospitalization and immediate treatment with IV antibiotics.

Skin, the largest organ in our body, can also be the source of a bacterial infection. Redness, swelling, warmth, pus, or pain occurs at the site of the infection. An infection may result from trauma to the skin or even a clogged pore that becomes an abscess. The infection can spread to the soft tissues beneath the skin (cellulitis). Sometimes the infection needs to be drained. Antibiotics are often needed. In addition, skin can react to some toxins by producing a skin rash; for example, the scarlatina rash that can occur after a Strep throat infection causes scarlet fever (skin rash is bright red and diffuse, with some skin that develops scaling and desquamation, or skin peeling off).

Fungal fever

Fungal infections can affect any organ system. Often a physician can identify these infections through a physical examination. Sometimes further testing is required and in rare instances, fungal fevers may require a biopsy to diagnose the infection. An antifungal medication will usually treat the infection.

Animal exposure fever

Certain people who work with animals can be exposed to rare bacteria that can cause fevers. In addition to the fever, the person may have chills, headache, and muscle and joint aches. These bacteria can exist in livestock, in unpasteurized dairy products, and in the urine of infected animals.

Travelers' fever

Anyone who travels, especially outside the United States, may develop fever after exposure to various new foods, toxins, insects, or vaccine-preventable diseases.

The only vaccines required by the U.S. and other countries for travelers at this time are for yellow fever and meningitis; these requirements depend on when and where people travel. Childhood vaccines such as those against measles, mumps, rubella, diphtheria, tetanus, and polio should be current prior to travel. Vaccines against hepatitis A, meningitis, and typhoid can be obtained before people travel to an area where exposure to those diseases is likely. The U.S. Centers for Disease Control and Prevention (CDC) can advise people on the current vaccines that are recommended or required for travel to various countries.

When traveling, consumption of contaminated water, uncooked vegetables, or unpasteurized dairy products can cause a low-grade fever and traveler's diarrhea. Bismuth subsalicylate (Pepto-Bismol), loperamide (Imodium), and certain antibiotics can help reduce symptoms but in some people may prolong the disease. The symptoms of abdominal cramping, nausea, vomiting, headache, and bloating should go away in three to six days. A fever higher than 101 F (38.3 C) or the presence of blood in the stool is an indication to go to a doctor immediately.

Insect bites are a common way that infections are spread in some countries. Malaria is a serious infection that can occur after a mosquito bite. The bitten person may have fevers that come and go every few days. A blood test must be done to make the diagnosis. In certain infected areas, a traveler can take medication to prevent malaria. Lyme disease is spread by the bite of a tick. This is common in areas of the U.S. where the deer tick is found. Any infection caused by an insect bite should be evaluated by a doctor.

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Fever of unknown origin (FUO) was defined in 1961 by Petersdorf and Beeson as the following: (1) a temperature greater than 38.3°C (101°F) on several occasions, (2) more than 3 weeks' duration of illness, and (3) failure to reach a diagnosis despite one week of inpatient investigation.